Transmission systems for electromagnetic waves, for example microwave and/or millimeter wave transmission systems, may include a phase shifter. Some embodiments of phase shifters comprise microstrips printed on a ferrite substrate. Some planar ferrite phase shifters create an elliptically polarized wave in a ferrite substrate, instead of a circularly polarized wave, thereby reducing the performance of the phase shifter. Other phase shifters are placed in metallized ferrite bars or ferrite-loaded waveguides, and/or incorporate thin quarter-wave plates at input and output ports to convert linear signals into circularly polarized signals. Such phase shifters may be expensive to manufacture.